The present invention is especially applicable to manufacturers of product that comprises a volume of a fluid composition dosed into a hand-holdable container. Without being prescriptive, the total volume of composition in such containers is typically between 5 and 1000 mls, though containers or either a larger or smaller volume may be contemplated, depending upon prevailing circumstances. The fluid compositions in such products normally contain one or more liquid components such as additives intended to impart a desirable characteristic to the composition. Many of these components or additives are each commonly present as a relatively small proportion of the overall composition, but for many reasons, it is desirable that it is dosed accurately into the composition. Some of the reasons are directly related to the nature of the component or additive, such as variation in product quality; for example if the additive is a fragrance, or a component of a fragrance, an incorrect dosage would alter the perceived smell of the product. Other reasons can have widespread applicability; for example many additives are relatively expensive, so that the total cost of the product can be increased inadvertently by even a small increase in the amount of additive added. The present invention is most desirably applicable in respect of dosing a component or only a small fraction of the composition into the container.
In one convenient method for manufacturers to fill containers or introduce one or more components into them, the container is conveyed to a filling station, is held there for long enough for filling and is thereafter removed to undergo a subsequent operation, such as capping or sealing the container. The maximum speed of a filling line is governed by the speed of the slowest operation which can have consequences as indicated below.
Apparatus has been described previously for conveying a fluid composition or component thereof into a container or onto the contents of a receptable through a nozzle in a dispensing head under pressure. Thus, for example, GB 2019813 describes a method and device for preparing beverages in portions, through two dispenser heads, possibly combined in a single unit, that are gently convergent. GB 2094758 describes related drinks apparatus in which two or possibly more nozzles direct jets of water at an acute angle into a cup to assist in the dissolution of a solid material, e.g. coffee or soup. GB 1481894 describes apparatus for the dispensing of syrup through a plurality of nozzles in a dispensing head onto an ice-cream substrate. EP 0216199 describes multi-orifice nozzle system having a variable pattern that is obtainable by independently oscillatable cylindrical cams, each bearing onto the cam surface of a needle valve to actuate or close the valve.
One method for making a product containing a fluid composition has been to prepare a large batch of the composition containing all its constituents in a vat and then withdraw a metered dose of that composition from the vat into the chosen container. This is a system that enjoyed widespread applicability because it is relatively simple to operate. It is relatively easy to mix large volumes of fluids to attain reasonable homogeneity and dose accuracy. Such a scale means that even comparatively small proportions of a constituent can be added quite accurately. For example, on a 10 tonne scale, 0.1% by weight constitutes 10 kg, which can be weighed quickly to an accuracy of better than 1%.
However, a batch manufacturing system is relatively inflexible to operate and includes a number of disadvantages that are becoming more applicable as consumers' habits and manufacturers' operational requirements change. There has been an increasing trend towards greater diversity in any single product, such as variations in the number of differently fragranced products offered to consumers to meet their individual preferences. Secondly, there is a trend for manufacturers to concentrate production at a smaller number of manufacturing sites. Both of these trends mean that there is a reduced likelihood that consecutive batches made in the same vat will have the same composition. When the composition of successive batches is different, it is necessary to clean out the vat and supply line to the filling station in order to avoid cross contamination between the two compositions. This can result in a significant down time between the production of the batches, and secondly there is a loss of the first composition which adhered to the vat wall and in the supply line. Both of these factors increase the average effective production cost of the manufacturer.
Accordingly, the instant inventor has been investigating how to reduce or circumvent the problems outlined above in batch manufacture. In one replacement method, the inventor contemplated introducing a liquid component of the composition directly into the eventual container. This, however, poses a different set of problems or difficulties. First, since the volume of composition to be introduced into a container is relatively small compared with the size of the batch, it is a significantly greater problem to dose an accurate weight of an individual component and especially an additive into the container compared with the entire batch. Secondly, dosing directly into the container can most easily be contemplated via a filling station on the filling line. The speed of the line dictates the length of the window whilst the container is under the filling station during which addition of the component can be carried out. Commonly, this is a relatively short period of time, often measured in fractions of a second. Though the window could be widened by moving the filling station at broadly the same speed as the line to keep both in register for longer, that in itself complicates the machinery, rendering it more expensive and introducing an extra risk of mechanical breakdown.
One method of dosing a measured amount of a liquid component comprises employing an accurate metering pump. Such pumps can be employed with a system in which a metered dose of the selected liquid component is expelled under pressure through a nozzle as a stream of liquid into a container that is held at a suitable orientation relative to the nozzle. These pumps are becoming more readily available, but their use is hindered by the fact that they have a relatively long response time. It is desirable to include sensing mechanism to detect the presence of a container at the dosing station in order to avoid wasteful discharge of the liquid component in the event that dosing and transport operations move out of synchronisation, especially in the context of fast line speeds and consequential short periods for dosing. Thus a slow response time of the pump can introduce considerable constraints on the line speed. Commonly, the speed of a dosing cycle is dictated by its slowest constituent element. Particularly in the case of dosing canisters, such as aerosol canisters, the use of an in-can dosing system based on such metering pumps would slow the filling line to such a great extent that the employment of such a system could not be countenanced commercially. The need remains to find a means to enable such accurate metering pumps to be employed.
In the course of the investigations leading to the instant invention, the inventor contemplated several modifications to the dosing system including increasing the pressure on fluid expelled through the nozzle, widening the nozzle diameter and inserting a mesh within the nozzle. Increasing the pressure on the liquid to the extent needed to compensate for the slow response time of the metering pump increases the linear velocity of the liquid to such an extent that it tends to break up the liquid into droplets when it encounters the base and/or side of the container into which it is being dosed, significantly increasing the risk that a variable fraction of the liquid will escape. This defeats the benefit achievable using an accurate metering pump.
A second possible variation comprises widening the nozzle, and at face value this would be attractive, because it would widen the diameter of the stream of liquid and thereby could permit a greater flow rate without significantly increasing the linear velocity of the flow. Unfortunately, this also was found to result in a reduction in the accuracy of dosing the liquid. Two causes of inaccuracy were identified, though there may be others. First, the use of a wider nozzle altered the overall shape of the stream, producing a longer tail after the control valve has been closed. In a tail, the diameter of the stream has become narrowed so that the volume flow is markedly reduced compared with that prevailing when the valve is open. Secondly, a wider nozzle encouraged the entrainment of bubbles of gas within the liquid and the formation of latent drips from the tip of the nozzle that continued noticeably after the control valve was closed. In an attempt to ameliorate this problem, the inventor inserted a mesh within the widened nozzle, but instead of curing the problem, in some ways the mesh even made it worse. The mesh actually increased to tail. Accordingly, the problem still remained as to how to accommodate a metering pump with a long response time.
It will be recognised that none of the patent specifications mentioned above contemplate or address such a problem.
It is an object of the present invention to identify a process and apparatus that can overcome or ameliorate one or more of the problems identified hereinbefore to improve in-container dosing of a liquid component into a container.
It is a further object of certain preferred embodiments of the present invention to improve the dosing of a small volume of liquid into a dispensing container on a high speed filling line.